$sockbr
From Scriptwiki
$sockbr is set to the number of bytes read by a /sockread command. It is used to test whether any information was in fact read from the buffer.
Example
on 1:sockread:testing:{
if ($sockerr > 0) return
:nextread
sockread %temp
if ($sockbr == 0) return
if (%temp == $null) %temp = -
echo 4 %temp
goto nextread
}
